Context: Intentional weight loss through dieting may adversely affect bone health. Whether testosterone treatment in men can prevent this is unknown.
Objective: To assess the effect of testosterone treatment on bone remodelling markers and bone density in dieting obese men.
Design, Setting and Participants: We conducted a pre-specified secondary analysis of a randomized double-blind, placebo-controlled clinical trial at an Academic centre. Obese men (body mass index > 30 kg/m2) with a total testosterone level <12nmol/L were enrolled.
Intervention: One hundred participants aged 53 years (interquartile range 47-60) receiving 10 weeks of a very low energy diet (VLED) followed by 46 weeks of weight maintenance were randomly assigned at baseline to 56 weeks of intramuscular testosterone undecanoate (n= 49, cases) or matching placebo (n= 51, controls). Eighty-two men completed the study.
Main outcome measures: The pre-specified outcomes were the between-group differences (mean adjusted difference, MAD) in serum c-telopeptide (CTx), N-terminal propeptide of type 1 procollagen (P1NP) and bone mineral density (BMD) at the lumbar spine and femoral neck.
Results:
At trial end, CTx was significantly reduced in men receiving testosterone compared to placebo, MAD -66ng/L (95% CI -113, -19), p=0.018, and this was apparent already after the 10 week VLED phase, MAD -63ng/L (95% CI -108, -18), p=0.018. By contrast, P1NP was marginally increased after VLED, MAD +4.2ug/L (95% CI -0.01, +8.4), p=0.057 but lower at study end, MAD -5.6ug/L (95% CI -10.1, -1.1), p=0.030 with testosterone treatment. No significant changes in sclerostin, lumbar spine BMD or femoral neck BMD were seen.
Conclusions:
In obese men with low testosterone levels undergoing weight loss, bone remodelling is modulated in a way expected to have favourable effects in bone mass. Larger trials are required to determine whether testosterone treatment can mitigate of diet-associated bone loss.